After a long, harsh winter in most provinces, Canadians may need to prepare themselves for a bad allergy season. Then again, it may not be as terrible as we fear.

Botany and allergy experts say it's hard to predict what the trees will do.

Once winter is over, trees release pollen spores. "It's the way trees have sex," explains Marian Munro, curator of botany at the Nova Scotia Museum in Halifax.

Some years, the trees produce more pollen, releasing a lot of it in a short period of time. A large dose of pollen all at once can trigger peoples' allergies. 

But it's impossible to know for sure what's going to happen this spring.

An allergy to pollen is activated when a "person's immune system goes awry," says Dr. Sandeep (Sandy) Kapur, an immunologist who works at the Halifax Allergy and Asthma Clinic.

"It's not well understood why the immune system does this but we do understand why it's uncomfortable for patients."

Kapur says an allergy to pollen can vary from being a annoyance to a serious condition. "When you go around feeling like you have a cold for a few weeks, it can really tire you out, especially if you have to write exams at this time of year."

Dr. Sandy Kapour

Over the past few generations, more children have been diagnosed with allergies and food sensitivities, says Dr. Sandy Kapur. (Halifax Allergy & Asthma)

He says a pollen allergy is rarely life threatening.

"We definitely have been seeing an increase in the number of people who have such allergies."Over the past few generations, more children have been diagnosed with allergies and food sensitivities.

It's not known what has caused the jump in allergies. One theory, Kapur says, is that over the last few decades, families have moved away from farms, where they would have been exposed to a wide variety of dirt and bacteria, and into cleaner dwellings in the city. Therefore, kids in early life are no longer exposed to things that naturally help boost their immune systems.

Kapur says a few people have come into the clinic so far this spring to talk about their pollen allergy. He advises them to get their allergy treatment plan in place and start early to be prepared.

Munro points out that it's only the trees that pollinate through the wind that will be bothering people at this time of year. Birch, beech, maple, oak, ash, willow and poplar are the most common varieties of trees releasing pollen that cause allergies.

Trees that pollinate using insects don't activate an allergic reaction.

She says coming up a bit later in the season, people with grass allergies will start to feel it.

Then later in the season, ragweed starts bothering people in late summer and early fall.

"A ragweed plant can release one billion pollen grains," says Munro.